3D Mold For Manufacturing Of Sub-Micron 3D Structures Using 2-D Photon Lithography And Nanoimprinting And Process Thereof

ABSTRACT

A process to manufacture a 3D mold to fabricate a high-throughput and low cost sub-micron 3D structure product is disclosed. The process integrates use of 2-photon laser lithography and 3D write technology to make a 3D mold of each layer of the 3D structure product, and then use nanoimprinting to form a sheet of polymer film of each layer of the 3D structure from the said 3D mold of that layer. Each layer of the sheet of polymer film is then fabricated into the sub-micron 3D structure product. The 3D mold of each layer of a high-throughput and low cost sub-micron 3D structure product, is further used to make master molds which is then used to form a sheet of polymer film of each layer of the 3D structure to fabricate the sub-micron 3D structure product. Applications using this process are also disclosed.

FIELD OF INVENTION

The present invention relates to a 3D mold for manufacture of sub-micron3D structures using a process which integrates 2-photon lithography andnanoimprinting to manufacture high-throughput and low cost sub-micron 3Dstructures.

BACKGROUND

Two-photon lithography is a very powerful, yet simple technique toproduce complex, three-dimensional structure from a liquid,photosensitive material. Two-photon polymerization (TPP) is based on thesimultaneous absorption of two photons, which induce chemical reactionsbetween starter molecules and monomers within a transparent matrix. Theabsorption of 2 photons requires extremely high peak intensities, thusan ultra-short pulse laser is needed to provide the high intensity.Previously, the most common application of two-photon absorption (TPA)has been two-photon confocal microscope where the fluorescence of a dyemolecule is observed after being excited by the means of TPA.Single-photon absorption used in standard photo- and stereolithograpictechniques is inherently two-dimensional, since ultra-violet light isabsorbed by the resin within the first few micrometers. Since thephotosensitive resins are transparent in the near-infrared (NIR) region,NIR laser pulses can be focused into the volume of the resin. As thelaser focus is moved three-dimensionally through the volume of theresin, the polymerization process is initiated along the path allowingthe fabrication of any 3D microstructure.

The rate of TPA is non-linear or quadratic dependent on incidentintensity, therefore making it possible to achieve lateral resolutionsbetter than 100 nm in the polymerized structures. For many applicationsthat requires 3D structures, such as tissue engineering scaffolds,biomedical implants, micro-lens, micro optics and other micro devices(MEMS) requires 3D resolutions in a few microns, the TPP process offer afast and simple way to achieve the desired resolutions.

Nanoimprint Technology

The principle of nanoimprint is straightforward. A schematic of theprocess developed in the original NIL process is shown in FIG. 3. A hardmold that contains micron—nanoscale surface relief features is pressedinto a polymeric material cast on a substrate at a controlledtemperature and pressure, thereby creating a thickness contrast in thepolymeric material. A thin residual layer of polymeric material is leftunderneath the mold protrusions and acts as a soft cushioning layer thatprevents direct impact of the hard mold on the substrate and effectivelyprotects the delicate nanoscale features on the mold surface. For mostapplications, this residual layer needs to be removed by an anisotropicO₂ plasma-etching process to complete the pattern definition.

A variation of nanoimprint has also been developed known as Step andFlash Imprint Lithography (SFIL) or UV nanoimprint lithography. In thistechnique, a transparent mold and UV-curable precursor liquid to definethe pattern is used, allowing the process to be carried out in roomtemperature, as illustrated below.

DISCUSSION OF PRIOR ART Use of 2-Photon Lithography in the Fabricationof 3D Template/Mold for Nanoimprint

Current NIL technologies rely on e-beam lithography, laser writers andoptical lithography technologies to write the designs of the device ontothe NIL templates. Unfortunately these technologies are inherent 2Dwriting technologies and are unable to fabricate 3D structures requiredby many NIL applications. Although current investigators get around thisproblem by a multi-layer processing, this is not an effective long termmanufacturing solution to obtain low cost 3D nanostructures. The stepsor effects of grayscale produced by multi-layer process are also notacceptable in many applications.

The proposed use of 2-photon lithography in nanoimprint templatefabrication is novel. For application with simple 3D requirements, suchas hemispherical structures, the stamping process could be performed ina single step, eliminating the need for a multi-stamping overlayprocess.

2-photon lithography has an extremely high write resolution (˜100 nm)compared to conventional laser writer (˜600 nm). Furthermore, similar toconventional laser writers, 2-photon lithography has comparatively highwriting speed compared to e-beam writers, making this technology idealfor most write applications except those that require resolutions lessthan 100 nm.

Use of 3D Nanoimprint in Tissue Engineering and Other Applications

Currently, there are no known groups working on the development oforgan/tissue scaffolds using 3D nanoimprint technologies. Stackinglayers of imprinted structures onto each other would make this rapidprototyping technique with the highest resolution and with comparativelyhigh throughputs. This process does not suffer as much materialconstrains compared to other rapid prototyping processes, as it relieson a physical stamping process to define its features.

Application of the technology developed under this invention could beused in fabricating unique photonics structures on polymer thin film togenerate functional film. An example of such film could be thefabrication of micro lens in the configuration. The advantage of havinga high resolution tool such as the 2-photon lithography tool tofabricate micro-lens is that curvature of the lens could be achievedusing very thin film. The advantages of such an approach are

-   -   1) lower material cost;    -   2) smooth lens surface would cause less lost of light; and    -   3) thinner use of polymer thin film will ensure less absorption        of light.

Although the NIL approaches have been designed to provide a solution tolithography in the next generation semiconductor wafer fabrication,scientist and engineers have been working on numerous applications inhybrid plastic electronics, organic electronics, novel Silicon devices,novel Gallium Arsenide devices, organic lasers, photonics, non-linearoptical polymer structures, high resolution organic light-emitting diode(OLED pixels), diffractive optical elements, broadband polarizer, harddisk drive, DNA manipulation, nanoscale protein patterning and cellculture. Currently, the NIL technology is used by the hard driveindustry in the fabrication of disk media.

The critical technical steps in NIL are separated into

-   -   1) mold fabrication,    -   2) resist, and    -   3) processes.

OBJECTIVE OF THE INVENTION

The inventive process uses a high-throughput sub-micron 3D structuretechnology which integrates multiple state of the art technologies,

-   -   [1] 2-photon lithography    -   [2] nanoimprint, and    -   [3] roll-to-roll nanoimprint.

By leveraging on the advantages of each technology it is possible toproduce sub-micron 3D structures at a low cost. This approach is similarto the approach in the semiconductor wafer manufacturing industry, wherethe integrated circuit on a silicon wafer is manufactured, using manyexpensive capital equipment for high volume production while reducingthe cost of each individual component.

The technology of this inventive process deviates from conventional NILtechnology right from the mold fabrication step. Conventional NILtemplates are patterned using e-beam lithography or optical lithography,fundamentally these patterning technologies are 2D in nature. However,the inventive proposes the use of 2-photon lithography and a 3D writetechnology to pattern the template. The patterned mold would be 3D.

SUMMARY OF THE INVENTION

A first object of the invention is a process to manufacture a 3D mold tofabricate a high-throughput and low cost sub-micron 3D structureproduct, the said process integrating 2-photon lithography andnanoimprinting, characterized by the use of 2-photon laser lithographyand 3D write technology to make a 3D mold of each layer of the 3Dstructure product and using nanoimprinting to form a sheet of polymerfilm of each layer of the 3D structure from the said 3D mold of thatlayer, fabricating each layer to make the sub-micron 3D structureproduct.

A second object of the invention is a 3D mold of a layer of ahigh-throughput and low cost sub-micron 3D structure product, whereinthe 3D mold of the layer is created by using 2-photon laser lithographyand 3D write technology to make a 3D mold of each layer of the 3Dstructure product and using nanoimprinting to form a sheet of polymerfilm of each layer of the 3D structure to make the 3D mold of that layerof the sub-micron 3D structure product.

Preferably, the 3D mold of a layer of a high-throughput and low-costsub-micron 3D structure product uses a process which integrates 2-photonlithography and nanoimprinting as claimed in any of the precedingclaims, wherein the 3D mold of the layer is manufactured as follows:—

-   -   creating a design of a 3D layer of the 3D structure;    -   setting up a writing process to produce an 3D image of the layer        of the 3D structure product using a 2-photon lithography tool;    -   developing a photo resist/polymer of the 3D image of the layer        on a substrate;    -   sputtering one or more layers of metal onto the surface of the        photoresist/polymer of the 3D image of the layer to form a seed        metal layer;    -   transferring the 3D polymer image coated with the seed metal        layer by an electroplating process to form a 3D metal mold;        wherein the 3D metal mold will be used to manufacture copy of        the 3D image of the same layer of the 3D structure product.

Advantageously, the step of creating a design of a mold of a 3D layer ofthe sub-micron 3D structure product includes anchoring the base of 3DCAD at the surface of the substrate, compensating for polymer shrinkingand making it mechanically strong to prevent the sub micron 3D structurefrom collapsing during the rinsing and drying process.

Advantageously in the step of setting up a writing process to produce amold of a 3D layer, the 3D image of each layer is an image from 0.01micron to 150 microns thickness.

Advantageously for the step of setting up a writing process to produce amold of a 3D layer, the 3D image of each layer is preferably an image of100 microns thickness.

Advantageously, for the step of setting up a writing process to producea mold of a 3D layer, the parameters of each layer from 0.01 microns to100 microns thickness is used as input for the manufacture of a mold ofthat layer.

Advantageously, for the step of setting up a writing process to producea mold of a 3D layer. the parameters of each layer is preferably 100microns is used as input for the manufacture of a mold of that layer.

Preferably, each layer of the 3D image is from 0.01 microns to 150microns.

Advantageously, for the step of developing a photo resist/polymer of the3D image of the layer on a substrate, the step includes cleaning thesubstrate, applying a spin coat resist onto the substrate, removing anyphoto resist on the back of the substrate with a solvent, pre-baking thesubstrate, if necessary, placing the substrate on a vacuum chuck,turning on the vacuum, aligning a wafer, inputting the correct processparameters, marking and checking the substrate to ensure that everydevice is correctly positioned and removing the photo resist/polymer ofthe slice of the image of that layer of the substrate.

Advantageously for the step of forming a seed metal layer by sputteringone or more layers of metal onto the surface of the resist/polymer ofthe image, the step includes checking there are no residues ofphotoresist or other materials left on the substrate, placing the waferin a sputtering tool, pumping the chamber down to base pressure,performing a short plasma clean process to ensure the surface is clean,depositing one or more metallic layers, layer by layer to form the seedmetal layer and removing the wafer from the chamber.

Advantageously, for the step of transferring of the polymer image formedfrom the seed metal layer by an electroplating process to form a metalmold, the step includes placing the substrate with the seed metal layerin an electroplating bath, setting the electroplating parameters,plating until the desired thickness is achieved, removing the wafer fromthe holder, removing the resist from the 3D mold, rinsing the moldthoroughly with de ionized water, grinding the back and edges of the 3Dmold to size, rinsing the 3D mold in de ionized water, performing O₂plasma cleaning on the surface of the 3D mold.

Advantageously, for the step of transferring of the polymer image formedfrom the seed metal layer by an electroplating process to form a metalmold, the step includes placing the substrate with the seed metal layerin an electroplating bath, setting the electroplating parameters,plating until the desired thickness is achieved, removing the wafer fromthe holder, removing the resist from the 3D mold, rinsing the moldthoroughly with de ionized water, cutting the back and edges of the 3Dmold to size, rinsing the 3D mold in de ionized water, performing O₂plasma cleaning on the surface of the 3D mold.

Advantageously for the step of transferring of the polymer image formedfrom the seed metal layer by an electroplating process to form a metalmold, the step includes placing the substrate with the seed metal layerin an electroplating bath, setting the electroplating parameters,plating until the desired thickness is achieved, removing the wafer fromthe holder, removing the resist from the 3D mold, rinsing the moldthoroughly with de ionized water, punching the back and edges of the 3Dmold to size, rinsing the 3D mold in de ionized water, performing O₂plasma cleaning on the surface of the 3D mold.

Advantageously for the step of fabricating a mold, the step includescoating a substrate with photoresist, setting the process parameters forthe stamping tool, transferring the 3D image from the metal mold onto alarge substrate through a series of stamp and step sequence, developingthe resist after processing, de-laminating the resist/polymer from thesubstrate, wrapping the substrate over a jig to form a cylinder,electroplating the cylinder until the desired thickness is achieved,grinding and polishing the cylinder to the correct finish and thickness,

Advantageously the step of fabricating a mold includes a master mold andsecondary molds.

Advantageously, for the step of fabricating a mold, a mold is made foran upper surface of a layer of a 3D structure and another mold is madefor a lower surface of the same layer of a 3D structure, and each layeris then aligned and zipped together to adhere together to form multiplelayer structures.

Advantageously, for the step of using the molds in a nanoimprintingprocess, the nanoimprinting process includes Thermal NIL or UV NIL orRoll-to-roll NIL.

Preferably, for the fabrication of the 3D mold, the 2-photon lithographyuses proprietary software to fabricate 3D molds of any shape and moldsof different shapes which can be combined to form complex molds.

Preferably, for the fabrication of the 3D mold, the initial template is3D in shape (hemispherical or other shape with curved side walls)compared to typical grayscale structures, which has vertical or slopingside walls.

Preferably, for the 3D mold, the mold made of flexible polymer isattached onto the surface of a cylinder to form a roller of flexiblepolymer mold, for nanoimprinting.

Preferably, for the 3D mold, the mold made of sheet metal is attachedonto the surface of a cylinder to form a roller of sheet metal mold withpolymer features, for nanoimprinting.

Preferably, for the 3D mold, the mold made of sheet aluminum is attachedonto the surface of a cylinder to form a roller of sheet aluminum moldwith metal features stamped on using a nickel master mold, fornanoimprinting.

Preferably, for the 3D mold, the mold made of sheet metal having metalfeatures electroplated onto its surface is attached onto the surface ofa cylinder to form a roller of sheet metal mold with metal features, fornanoimprinting.

Preferably, the process of fabricating a 3D mold follows the NIL processflow, and includes:—.

-   -   improved designs in mold manufacturing with library of shapes to        establish design rules for mass manufacturing of 3D devices,        making molds with these 3D templates    -   use of the stamp on NIL thermal, UV, stamping and roll-to-roll        technology

A third object of the invention is a system to manufacture a 3D mold tofabricate a high-throughput and low cost sub-micron 3D structureproduct, the said system integrating 2-photon lithography andnanoimprinting characterized by the use of 2-photon laser lithographyand 3D write technology to make a 3D mold of each layer of the 3Dstructure and using nanoimprinting to form a sheet of polymer film ofeach layer of the 3D structure from the 3D mold, and stacking each layerof the 3D structure to fabricate the sub-micron 3D structure product.

Preferably, the system to manufacture a 3D mold to fabricate ahigh-throughput and low cost sub-micron 3D structure products uses 3Dwrite technology to pattern a template for the 3D mold.

Preferably, the system to manufacture high-throughput and low costsub-micron 3D structure products uses nanoimprinting which is ThermalNIL thermal or UV NIL or Roll-to-Roll nanoimprinting.

A fourth object of the invention is a plurality of 3D molds to fabricateorgan/tissue scaffolds, wherein plurality of layers of images of 3Dstructures of whole organ scaffolds of complex organs such as kidney orliver, are created, including the following:—

-   -   a. Organ/tissue scaffolds fabricated by slicing a 3D CAD design        of the scaffold into multiple layers, each layer being        individually fabricated using nanoimprint to overlay and bond        all layers to form the final scaffolds, creating such scaffolds        which are anatomically similar to those created in vivo physical        environment.    -   b. Tissue engineering scaffolds.    -   c. Fabrication of medical implantable devices

A fifth object of the invention is a 3D mold is to fabricate simple 3Dstructures such as sinusoidal structures and hemispheres in a singlepass, wherein a single stamping nanoimprinting process is used in themanufacture of photonics, LCD industry, holographic tags, micro lens forfocusing, bandages.

Preferably, for the 3D mold to fabricate simple 3D structures, thematerial used in the NIL process could be either synthetic or biologicalmaterial.

A sixth object of the invention is a plurality of 3D molds formanufacture of scaffolds for tissue engineering, comprising thefollowing steps:—

-   -   a. creating a 3D template using 2-photon lithography.    -   b. transferring the 3D image onto a 3D mold by electroforming or        any type of forming techniques, such as e-beam lithography or        optical lithograph, depending on the type of molds (flexible,        hard, size, surface properties, and resolution) needed for the        processing.    -   c. designing the structures with a computer aided design program        (CAD).    -   d. using proprietary software with the 3D CAD drawing as input        to automatically slice the said structures into multiple layers.    -   e. eliminating layers with repeated patterns.    -   f. fabricating templates for mold making.    -   g. fabricating a master mold for each layer to produce a        hard/flexible mold for a stamping/roll-to-roll nanoimprint tool.    -   h. sandwiching each layer produced onto each other to form a        complete organ scaffold with physical dimensions close to an        actual natural scaffold.

A seventh object of the invention is a 3D mold for manufacture ofmedical devices such as bridges for nerves and bones requiring physicalcues to guide growth of nerves and bones, comprising the followingsteps:—

-   -   a. creating a 3D template using 2-photon lithography.    -   b. transferring the 3D image onto a mold by electroforming or        any type of forming techniques, such as e-beam lithography or        optical lithograph depending on the type of molds (flexible,        hard, size, surface properties, and resolution) needed for the        processing.    -   c. designing the structures with a computer aided design program        (CAD).    -   d. using proprietary software with the 3D CAD drawing as input        to automatically slice the said structures into multiple layers.    -   e. eliminating layers with repeated patterns.    -   f. fabricating templates for mold making.    -   g. fabricating a master mold for each layer to produce a        hard/flexible mold for a stamping/roll-to-roll nanoimprint tool.    -   h. sandwiching each layer produced onto each other to form a        complete organ scaffold with physical dimensions close to an        actual natural scaffold.

An eighth object of the invention is a 3D mold for manufacture ofcustomized micro-lens to form a more functional optical film, comprisingthe following steps:—

-   -   a. creating a 3D template using 2-photon lithography.    -   b. transferring the 3D image onto a mold by electroforming or        any type of forming techniques, such as e-beam lithography or        optical lithograph, depending on the type of molds (flexible,        hard, size, surface properties, and resolution) needed for the        processing.    -   c. designing the structures with a computer aided design program        (CAD).    -   d. using proprietary software with the 3D CAD drawing as input        to automatically slice the said structures into multiple layers.    -   e. eliminating layers with repeated patterns.    -   f. fabricating templates for mold making.    -   g. fabricating a master mold for each layer to produce a        hard/flexible mold for a stamping/roll-to-roll nanoimprint tool.    -   h. sandwiching each layer produced onto each other to form a        complete optical film made entirely of compound micro-lens with        custom designed curvatures        wherein the optical film can be incorporated onto the surface of        a thin film or a thin layer of glass to reduce reflection, total        internal reflection, collect light and focus the light collected        onto active devices.

These and other objects of the invention will no doubt become obvious tothose of ordinary skill in the art after reading the following detaileddescription which follows, and which may be learned by practice of theinvention by those skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings which are incorporated in and constitute apart of the specification illustrate examples of the processes referredto in the invention and together with the general description, serve toexplain the principles of the invention.

FIG. 1 is a process flow of the steps in fabricating a sub micron 3Dmold of this inventive process.

FIG. 2 is a process flow for the first step of creating 3D CAD designsas inputs into the 2-photon lithography step of this inventive process.

FIG. 3 is a process flow for setting up the 2-photon lithography toolfor the step of writing in this inventive process.

FIG. 4 is a process flow for the preparation of a substrate for the stepof 2-photon lithography scanning in this inventive process.

FIG. 5 is a process flow for the step of developing a photo resist inthis inventive process.

FIG. 6 is a step of forming a seed metal layer which is sputtered ontothe surface of the resist/polymer in this inventive process.

FIG. 7 is the step of metallization to form a metal mold of thisinventive process wherein the transfer of the polymer image is carriedout using an electroplating process using a seed metal layer which issputtered onto the surface of the resist/polymer.

FIG. 8 is a step of fabricating the secondary mold in this inventiveprocess.

FIG. 9 is a step of fabricating the roller NIL molds in this inventiveprocess.

FIG. 10 is an illustration of a process flow for making a flexiblepolymer mold or template.

FIG. 11 is an illustration of a process flow for making a metal mold ortemplate using physical stamping of an aluminum sheet.

FIG. 12 is an illustration of a process flow for making a sheet metalmold or template with metal features electroplated onto the surface.

FIG. 13 is an illustration of a process flow for making a sheet metalmold or template with polymer features.

FIG. 14 is an illustration of a nano-imprinted polymer film ofmicro-lens in the manufacture of a side emitting thin film layer.

DETAILED DESCRIPTION OF THE INVENTION

The process flow of the steps in fabricating a sub micron 3D mold ofthis inventive process is shown in FIG. 1. The general process procedureand steps are as follows:—

-   -   1) 3D CAD designs are input into the 2-photon lithography step        of this inventive process.    -   2) The files are then pre-processed by the tool software, where        the 3D design is sliced into layers 100 nm thick.    -   3) Each layer is then scanned onto the surface of        wafers/substrate coated with resists.    -   4) The resist is then developed.    -   5) A metal seed layer is next deposited onto the resist        template.    -   6) An electroplating step then follows.    -   7) Mold is now ready for stamping or to be use as a master mold        to produce secondary mold or roller imprint molds

FIG. 2 to FIG. 9 illustrates each of the steps in the general processprocedure.

FIG. 2 is a process flow for the first step of creating 3D CAD designsas inputs into the 2-photon lithography of this invention. The designsof 3D structures are created and exported as 3D designs in STL fileformat in the following manner:—

-   -   1) Mechanical 3D designs, structures could be drafted using 3D        CAD programs which is known in the art.    -   2) Design rules that has to be followed.        -   a. The base of the 3D design will have to be anchored at the            surface of the substrate; this is to prevent the structure            from drifting during marking.        -   b. The structure will have to be designed such that the            solvent used in the development process is able to remove            unexposed polymer.        -   c. The structure will have to be designed such that it will            be able to compensate for polymer shrinking after            development.        -   d. The structure will have to be mechanically strong, to            prevent device collapsing during the rising and drying            process.

These designs of 3D structures are exported as STL file format forfurther processing

FIG. 3 is a process flow for setting up the 2-photon lithography toolfor the step of writing in this inventive process. What is describedherein is a generic process and some process steps will be eliminated oradded to meet specific requirements:—

-   -   1) First the STL file with the 3D CAD design is imported into        the customized laser scanning software known in the art.    -   2) Next the size of the image is corrected to ensure that the        image input into customized laser scanning software is correctly        scaled to the correct physical size.    -   3) Input position of laser focus into system to provide initial        wafer alignments    -   4) Slice the image into 100 nm thick slices. (this thickness        could be varied based on the desired resolution of final device)    -   5) Input the correct parameter for polymer used in process.        -   a. Power of laser—essentially controls the resolution and            scanning time of the job.        -   b. Scan speed—The scan speed will impact on the resolution            (spot size)        -   c. Correction files—This is determined by the type of lens            and polymer being used for the job. By selecting the correct            correction file, image distortion will be minimized.        -   d. Wobble—By wobbling the laser the effective spot size of            the laser can be increased. This will increase the            throughput of the system, as well as providing different            texture on the surface of fabricated devices.        -   e. Hatching—Hatching will determine the number of line scan            that will be performed to fill an area that needs to be            filled. Varying the hatching pattern will also affect the            surface texture of the fabricated device.        -   f. Other factors that will affect the scanned device—Jump            speed (corner sharpness), acceleration (consistent line            thickness), field size (a larger scanning field would mean            that the device would be more prone to distortion at the            edge of field), docking position of the laser (if            incorrectly docked, the scattered laser light would            partially polymerize resists), stepping size (gap and street            between structure, will also affect the stitching of larger            devices), stepping pattern (affect device to device            accuracy).

FIG. 4 is a process flow for the preparation of substrate for the2-photon lithography scanning. The selection of substrate type willdepend on the type of stamping tool used for the production of secondarymold, device fabrication. For thermal NIL a standard siliconsubstrate/process is sufficient and is the process of choice as siliconwafers typically have the best surface (low root-mean-squared roughnessand flatness) for laser writing. For SFIL, a transparent substrate willbe required such as a glass wafer or substrate.

The choice of substrate will affect the scanning process, due to thesedifferences:—

a) adhesion layers will have to be used,b) glass has less reflection and a higher scanning power is required,c) glass wafers are not as flat as silicon wafer and the laser scanningprocess might produce poor yields.

With reference to the process flow of FIG. 4, a generic silicon processwill be described. Some modifications will be needed for other types ofsubstrate.

-   -   1) Depending on the final application different substrates could        be loaded into the tool.        -   a. Silicon for most thermal NIL processes        -   b. Glass and other transparent substrate for SFIL            applications    -   2) For silicon wafer perform a piranha clean (using a hot        sulfuric acid cleaning process such as described in “Silicon        Processing for the VSLI Era Vol. 1—Process Technology Chapter 15        “Wet Processing: Cleaning and Etching” by Stanley Wolf & Richard        N Tauber, 1986 Lattice Press)    -   3) For glass substrate, dip wafer into dilute Hydrofluoric Acid        for 30 seconds and rinse with de-ionized (“DI”) water for 2 min.        Blow dry the substrate and glass substrate is ready for use.    -   4) Spin coat/evaporate correct adhesion layer (depending on the        resist and substrate type, this could differ) onto the        substrate.    -   5) Spin coat correct resist onto the substrate. Once again this        could differ significantly depending on applications.    -   6) Remove any photo resist that is on the back side of the        substrate with correct solvent.    -   7) Pre bake the substrate, if necessary. (This would drive out        the excess solvent and minimize shrinkage of structure after        processing).    -   8) Place substrate on vacuum chuck and turn on the vacuum.    -   9) Home the stage.    -   10) Align wafer, input correct process parameters for the        correct substrate type, photo resists.    -   11) Start the marking process.    -   12) After the process has been completed, check the substrate to        ensure that every device is correctly positioned with the built        in contrast feature of the 2-photon lithography tool.    -   13) Finally remove the substrate for resist developing.

FIG. 5 illustrates a process flow for developing a photo resist in thisinventive process. The process flow for photo resist developing isdifferent for different types of resist. The process flow describedbelow is for PMMA based photo resist on glass or silicon wafers. Thedeveloper used could be modified with other chemicals depending on theapplication, thickness, and the marking process.

Other precaution that has to be taken would be to ensure that the dryingprocess of 3D device does not cause the devices to collapse, andstandard MEMS processing techniques such as critical point drying of thesubstrate will have to be performed.

-   -   1) Place the wafer into a wafer holder.    -   2) Dip the wafer into the developer. This could vary based on        type of photoresist being used.    -   3) The soak time of the wafer in developer depends on the        thickness of the photo resist being used and if there are deep        undercuts in the design.    -   4) After soaking the wafer in the developer for a sufficient        length of time, dip wafer into fresh developer for another 1        hour.    -   5) Rinse the wafer with correct solvent or with DI water.    -   6) And finally allowing the wafer to dry. Either with a spin        drying process, air dry or critical point drying.    -   7) The sample is now ready for further processing.

Depending on the applications of mold, the mold developed at this stagecould be used for stamping, e.g. simple NIL research and developmentapplications. For most applications, a metal mold such as nickel wouldbe needed.

FIG. 6 is a step of forming a seed metal layer which is sputtered ontothe surface of the resist/polymer of this inventive process. This stepof seeding leads up to the step of metallization wherein the transfer ofthe polymer image is carried out using an electroplating process Thetransfer of the polymer image to the metal mold is done with anelectroplating process. Unfortunately the polymer coated surface of thesubstrate is not conductive and will not be a good electrode forelectroplating. Consequently, a seed metal layer of or nickel isrequired to be either sputtered or evaporated onto the surface of theresist/polymer.

A typical step of forming the seed layer process is described in theprocess flow with reference to FIG. 6.

-   -   1) Ensure that there are no residues from the previous process        step.    -   2) Place the wafer in an evaporation tool or sputtering tool.    -   3) Pump the chamber down to base pressure.    -   4) Perform a short plasma clean process to ensure surface is        clean.    -   5) Deposit 20 nm thick Titanium layer    -   6) Next followed by a 300 nm thick layer of gold.    -   7) Remove wafer from chamber.

The substrate is now ready for electroplating.

FIG. 7 is the step of metallization to form a metal mold of thisinventive process wherein the transfer of the polymer image is carriedout using an electroplating process using a seed metal layer which hasbeen sputtered onto the surface of the resist/polymer. The metal mold isformed entirely by an electroplating process, which is described inthese steps, with reference to FIG. 7:—

-   -   1) The substrate with the seed metal layer is placed in the        electroplating bath.    -   2) Next set the electroplating parameters.    -   3) Over plate until desired thickness—typically in the range of        3-5 mm.    -   4) Remove wafer from holder.    -   5) Remove the resist from the mold. This could be typically        performed with a resist stripper or hot acetone. At this point        the silicon/glass substrate will be removed.    -   6) Rinse the mold thoroughly with DI water.    -   7) Next grind the back and edges of the mold to size.    -   8) Rinse the mold in DI water.    -   9) Perform O₂ plasma clean on the surface of mold.

The mold is now ready for use. Typical mold size would be about 4 mm×20mm in size and would not be suitable for use for high throughputapplications. Such applications would have to use the mold to producefunctional raw materials (functional films). In this case a secondarymold would be needed. The fabrication of such a secondary mold will bedescribed in details below.

FIG. 8 is a step of fabricating the secondary mold in this inventiveprocess. For many applications, the pattern required by the user isperiodic (repeated). The write time for the 2-photon lithography tool islong and expensive. To minimize the write time, the master mold will beused to produce a larger secondary mold by using a stamping tool, forthe following reasons:—

-   -   1) By using the 3D master mold produced with the 2-photon        lithography tool and stamping onto a resist/polymer coated        substrate, a much larger mold could be fabricated. This would        help reduce the necessary write time to replicate a large mold.    -   2) Reduce any chance of error.    -   3) Increase yield.    -   4) Very large surface area could be produced fairly quickly.

The process flow for the step of fabricating the secondary mold isdescribed below with reference to FIG. 8:—

-   -   1) First spin coat a suitable resists/polymer onto the surface        of a substrate. This substrate could be silicon wafer, large        sheet of polymer, sheet metal, glass. (Depending on the        applications of the final product.)    -   2) Depending on the type of substrate and resists used in the        process, key in the correct parameters of the stamping process        into embossing/stamping tool.    -   3) Load the master mold into a stamping tool and start stepping        the pattern over the entire substrate.    -   4) Next the patterned substrate is developed and a seed metal        layer is sputtered over the pattern substrate.    -   5) The substrate is then dipped into an electroplating bath and        over plated to the desired thickness.    -   6) The final device is then grinded to the correct thickness    -   7) Edge of the mold is also grinded to the correct thickness

By using the master mold to step over many times over a large area,technically molds that are fairly large (1 m²) can be fabricated.

For high throughput application and continuous fabrication of largesheets of functional polymer films, a roller mold could be fabricated.

FIG. 9 is a step of fabricating the roller NIL molds in this inventiveprocess. As explained in the earlier section large sheet of functionalmaterials might be needed for certain applications. Current methods ofimprint large surface areas are achieved through the use of rollerimprinter, where a roller with nanometer scales 3D features iscontinuously used to mold a large continuous sheet of polymer.

The step of fabricating the roller NIL mold is illustrated by referenceto FIG. 9.

-   1) First coat a suitable substrate with photo resist. Some of the    possible substrate could be PMMA films, sheet metal, silicon wafers,    glass etc.-   2) Next set the process parameter for the stamping tool.-   3) Transfer the 3D image from master mold onto the large substrate    through a series of stamp and step sequence.-   4) Develop resist after processing.-   5) De-laminate resist/polymer from substrate.-   6) Deposit a seed metal layer onto the surface of the substrate.-   7) Wrap the flexible substrate over a jig to form a cylinder.-   8) Electroplate cylinder till desired thickness. The minimum    thickness will have to be greater than 3 mm.-   9) Grind and polish the nickel cylinder to the correct finish and    thickness.-   10) Roller mold is now ready for use.

The invention can also cater for the manufacture of layers havingfeatures on both its upper layer and lower layer using 2 roller molds.In such applications, The 2 roller molds can be aligned on top of eachother. For simple 2 layer structures, a single pass through the doublemold will be sufficient. For more complex structures that require morelayers, each layer could be aligned by zipping it together. Thesestructures could be used to hold the film together and align thedifferent layers. The first layer and second layer will be aligned whenthey are zipped together. Each layer is then adhered onto each other toform multiple layer structures.

Fabrication of Flexible Molds

Flexible roller imprinter molds for nanoimprinting could be used for theimprinting of 3D structures. Flexible molds made of sheet metals orpolymers with features patterned on the surface could be wrapped arounda large roller as illustrated below:—

A large roller mold can be formed by attaching several flexible moldsonto the surface of the cylinder. This approach is fairly similar tooffset printing in the printing industry where aluminium sheets withphotosensitive chemicals are exposed to transfer the print image ontothe plate and attached onto the plate cylinder, as illustrated below:—

The flexible molds/plates are attached onto slits that are designed onthe surface of the roller and roughly aligned into position by notcheson the edges of the flexible mold/plates. Fine alignment is then done byadjusting the positions of the rollers and polymer feed. With this setupalignment accuracy of up to 10 microns or less with top and bottomimprinting can be achieved.

There are many ways a flexible mold could be created using the master 3Dmold created using 2-photon lithography:—

-   -   1) Flexible polymer mold;    -   2) Sheet metal mold with polymer features;    -   3) Sheet aluminium (soft metal) mold with metal feature stamped        on using a thicker master mold; and    -   4) Sheet metal mold that has metal features electroplated onto        surface

An example of a process flow using different types of flexible molds isdescribed in the following sections.

Process Flow for Making a Flexible Polymer Mold/Template

The process flow for making a flexible polymer mold/template isdescribed with reference to FIG. 10.

In this process a flexible mold that is made from a sheet metal orpolymer substrate can be produced.

-   -   1) First coat a suitable resists/polymer onto the surface of a        flexible substrate. This substrate could be a large sheet of        polymer or sheet metal. (depending on the applications of the        final product.)    -   2) Depending on the type of substrate and resists used in the        process, key in the correct parameters of the stamping process        into the stamping tool. The stamping process can either be a UV        imprinting process or thermal imprinting process or a        combination of both.    -   3) Load the master mold into a stamping tool and start stepping        the pattern over the entire substrate.    -   4) The polymer film can now be used as a secondary mold or as a        production mold wrapped over a roller.

Process Flow for Making a Metal Mold or Template Using Physical Stampingof an Aluminum Sheet.

The process flow for making a metal mold or template using physicalstamping of an aluminum sheet is described with reference to FIG. 11.

In this process a flexible mold is made from a sheet metal by physicallystamping onto a soft metal using a nickel mold.

-   -   1) Set the process parameter    -   2) Install the correct mold for stamping (mold will have to be        made from a harder metal such as nickel.    -   3) First load the sheet metal, into the stamping tool.    -   4) Proceed with the sample process.    -   5) The sheet metal can now be used as a secondary mold or as a        production mold wrapped over a roller.        Process Flow for Making a Sheet Metal Mold or Template with        Metal Features Electroplated onto the Surface.

The process flow for making a sheet metal mold or template with metalfeatures electroplated onto the surface is described with reference toFIG. 12 and is as follows:—

-   -   1) Coat photoresist onto the surface of sheet metal.    -   2) Input the correct process parameters.    -   3) Load 3D mold into the stamping tools.    -   4) Load sheet metal into tool.    -   5) Proceed with stamping process.    -   6) Deposit seed metal or apply a clean step to expose the sheet        metal at the bottom of the polymer structure for electroplating.    -   7) Perform electroplating.    -   8) Strip and remove photoresist from metal sheet.        Process Flow for Making a Sheet Metal Mold or Template with        Polymer Features.

The process flow for making a sheet metal mold or template with polymerfeatures is described with reference to FIG. 13 and is as follows:—

-   -   1) Coat photoresist onto the surface of sheet metal.    -   2) Input the correct process parameters.    -   3) Load 3D mold into the stamping tools.    -   4) Load sheet metal into tool.    -   5) Proceed with stamping process.    -   6) Post process the polymer to harden the polymer.    -   7) The mold is ready for use.

Applications of the Inventive Process

A comparative advantages of the different fabrication technologies isshown in the matrix below. By combining 2-photon lithography andnanoimprint, the invention will enable mass-manufacture of devices at avery low cost compared to all the competing manufacturing technologies.

From the matrix of different fabrication technologies, it can be seenthat the inventive process is best suited for biological applications.The biological applications using this inventive process is fairlysimilar to clinical approaches to organ transplantation and existinggrafting techniques. Instead of using biomaterial scavenged fromcadavers, a totally synthetic scaffold is manufactured to minimizeissues of disease transmission, shortage of suitable cadavers and lowercost.

First a 3D template that is created using 2-photon lithography or othertypes of rapid prototyping technology (determined by the resolution offinal device) is created. Next the image is transferred onto a mold byelectroforming or any type of forming techniques, depending on the typeof molds (flexible, hard, size, surface properties, and resolution)needed for the processing. Products that only require a single stampingprocess could be then produced by either standard roll-to-rolltechnology or through standard NIL or UV NIL technologies.

The structures are designed with a computer aided design program (CAD).Next this 3D CAD drawing is input into proprietary software used for theinvention and automatically sliced into multiple layers. Layers withrepeated patterns are eliminated and templates for mold making arefabricated. With this template, a master mold for each layer isfabricated to produce a hard/flexible mold for a stamping/roll-to-rollnanoimprint tool.

For applications where a single imprint step is sufficient, such asholographic tags, micro lens for focusing, LCD, bandages, the finalproduct is packaged for sale. Other application that require morecomplex 3D structures could have each layers bonded onto each other toform a larger device such as a tissue scaffold, organ scaffold. Withthis inventive technology it is possible to produce an organ scaffold ata rate of 4/hour.

The manufacturing method includes a process for writing 3D templates fornanoimprint, through the use of 2-photon lithography. The initialtemplate is 3D in shape (hemispherical or other shape with curved sidewalls) compared to typical grayscale structures, which has vertical orsloping side walls.

The process for writing 3D templates for nanoimprint which is based onthe NIL process flow, includes:—

-   -   Improved designs in mold manufacturing using library of shapes        to establish design rules for mass manufacturing of 3D devices;    -   Making molds with these 3D templates; and    -   Use of the stamp on NIL thermal, UV, stamping and roll-to-roll        technology;

The method for fabrication of organ/tissue scaffolds using 2-photonlithography to create any type of 3D structures and nanoimprint tocreate whole organ scaffolds of complex organ such as kidney or liver,including the following:—

-   -   a. Organ/tissue scaffolds fabricated by slicing a 3D CAD design        of the scaffold into multiple layers. Each layer is individually        fabricated using nanoimprint and overlay and bonded forming the        final scaffolds. With this technique scaffolds that are        anatomically similar to in vivo physical environment is created.    -   b. Tissue engineering scaffolds, including plant tissue.    -   c. Fabrication of medical implantable devices.

The method for fabricating simple 3D structures, such as sinusoidalstructures and hemispheres, in a single pass, can be used in photonics,LCD industry, holographic tags, micro lens for focusing, bandages.

The method for fabricating simple 3D structures wherein the materialused in the NIL process could be either synthetic or biologicalmaterial.

This manufacturing technology can be used for organ/tissue engineeringscaffold fabrication.

The inventive process is the enabling technology for organ/tissueengineering and key innovations which are listed below.

Fabrication of Organ/Tissue Scaffolds with 3D Nanoimprint Technology

Conventional scaffolds methods for scaffold fabrication includetechniques such as solvent casting and particulate leaching, gasfoaming, fiber meshes and fiber bonding, phase separation, melt molding,emulsion freeze drying, solution casting and freeze drying. There areseveral limitations involving these processing techniques such as lackof precise control of pore sizes, pore geometry, pore interconnectivity,spatial distribution of pore, and construction of internal channelswithin the scaffolds. In addition many of these techniques exploitorganic solvents, like chloroform or methylene chloride as a part of theprocess to dissolve synthetic polymers. The presence of organic solventresidues is a significant problem of conventional fabrication methodsdue to toxins and carcinogens to which cells are exposed if residualsolvent exists.

An alternative approach to scaffold fabrication is through the use ofadvance manufacturing technologies/rapid prototyping (RP) technologiessuch stereolithography (SLA) selective laser sintering (SLS), 3Dprinting, fused deposition modeling (FDA) and 3D bioplotter. So far onlya few research groups have demonstrated the exploitation of RPtechnologies in clinical applications. Within bone tissue engineering,the SLS has proven its usefulness to fabricate polycaprolactonescaffolds. Also 3D printing has been used to create negative molds intowhich a polyactide solution can be poured and thermally phased andseparated to create nanofibrous scaffolds. The results of all biologicalstudies show that microporousity and very fine surface features improvebone growth into scaffolds by increasing surface area for proteinadsorption, increasing ionic solubility in the micro environment andproviding attachment points for osteoblasts. All mentioned RP approacheshave not yet lead to the construction of harmonically organized complextissues. This is due to the lack of print resolution of current RPtechnologies, difficulty in embedding various cell types withinintricate designs. The only technology capable of doing that right nowis organ printing, some structures have been printed by this setup,printing several cell types and biomaterials simultaneously. However,this setup is not suitable for fragile cell type such as hepatoctyes.Further, the inventor has found that the biomaterial used to print themixture obstructs cell-cell interaction required to maintain functionand differentiation. A matrix to compare the different type of scaffoldtechnologies is shown in Table below.

Nano- RP Conven- Invention imprint Technologies tional 1 Max. Resolution~100 nm <100 nm >1000 nm <100 nm 2 Material Range Large Large LimitedLarge 3 Custom shape Yes Limited Yes No 4 Complex organs Yes No No No 53D Yes Yes Yes No 6 Cost Low Low High Low 7 Scalability Yes Yes No YesTable showing Head-to-Head comparison of various scaffold fabricationtechnologies

Application of Inventive Process for Organ/Tissue Engineering

Tissue engineering is an essential technology in the emergingregenerative medicine industry. It can be defined as the engineering offunctional tissues and organs for the repair of diseased body parts.Autologous tissue engineered devices are formed by combiningpatient-derived cells with a degradable material and implanting thecombination in the body. The material is termed a scaffold or matrix. Itis porous or gelatinous in nature, ensuring the incorporation of cellswithin the substrate and not solely on the surface. The goal of tissueengineering is to circumvent the limitations of conventional clinicaltreatments for damaged tissue or organs based on the use of organtransplants or biomaterial implants. The most essential limitations ofthese treatments involve shortage of donor organs, chronic rejection andcell morbidity.

The dominant method of tissue engineering involves growing the relevantcells in vitro into a scaffold that attempts to mimic the function ofextracellular matrix. Without any three dimensional supportingstructures the cell will form a random two-dimensional mainly monolayerof cells. Thus the primary function of a scaffold serves as an adhesionsubstrate for the cell. In addition the scaffold provides temporarymechanical support and guidance to the growing tissue.

In recent years various researchers have relied on decellularizedorgans, heart and thorax, from cadavers to provide architecture,geometry and cellular constituents to build bioartificial organs. Thesescaffolds are reseeded with cells and cultured in a perfused bioreactorfor weeks and the resultant construct could perform some or mostfunctions of an organ. In other simple organs such as the cornea,bladder, skin and bone the organ scaffold matrix was replaced with atotally synthetic scaffold.

The clinical success in the reports from the previous paragraph suggeststhat the approach of providing 3D scaffold support is the best approachto regenerative medicine. However, to harvest scaffolds from cadavers isa serial process and have many issues associated with this technique,such as transmission of diseases, number of cadavers available, skilledsurgeons to extract the parts, ethical and quality control issues. Withthe inventive technology, a physiologically similar environment, andwith the correct chemical signals, totally synthetic organ/tissuescaffold could be recreated for regenerative medicine.

There is a clear need for the development of tissue engineered organs.However, the main problems for the engineering of more complex tissuesare angiogenesis, growing blood vessels to supply the new tissue withblood, and developing 3D matrices on which to grow new tissue.

The use of cheap, high throughput, high resolution and 3D manufacturingtechnology of the invention offers a solution to the problems faced byresearchers in developing a vascularized, 3D matrix. This would furtherthe cause of tissue engineering research and improve healthcare ingeneral. Other biomedical applications for these scaffolds, when used incell culture, could be used to develop better drug models forpharmaceutical companies to perform drug testing, lower the cost ofclinical trials, and drug development.

The inventive process has wide ranging applications, some of which arelisted below

3D technology Will 3D Will Invention Industry critical to technologyimprove improve size/Stage of Application/Industry industry? technology?technology? development 1 Organ/Tissue Yes Yes Yes PotentiallyEngineering Scaffold Large, Emerging 2 Hybrid Plastic/Organic No Yes YesLarge Emerging Electronics 3 Silicon/Gallium Arsenic No No No Large,Mature Devices 4 Organic Lasers No Yes Yes Potentially Large, Evolving 5Photonics Yes Yes Yes Large, Evolving 6 LCD No Yes Yes Large, Evolving 7Micro-fluidics No Yes Yes Potentially Large, Evolving 8 Biotech Yes YesYes Potentially Large, Evolving 9 Hard Drive No Yes No Large, MatureTable showing possible applications from technology developed under thisinvention.

The application of the invention to tissue engineering can be extendedto plants and agricultural sectors.

Application of Inventive Process to Manufacture of Micro-Lens

Controlling and modulating light can be done through a variety of waysusing refractive, diffractive, interference or reflective methods. Thiscan be carried through manipulating light through micro-lens. Micro-lensproduced by the inventive process can be designed to contour thesurface/interfaces of the lens to focus, reflect, guide and bend light.Through miniaturization of the lens systems, the bulk of most lensmaterial are removed, with improved transmission and efficiency sincethere are less signal attenuation, caused by bulk absorption. Theselenses are integrated into films to produce functional optical films.

Currently micro-lens are fabricated by molds formed by 1) melting moltenglass/photoresist/liquids and allowing the surface tension to form thesmooth spherical surfaces required for lens. 2) Other techniques involvethe repeated etching patterns to form arrays of multiple lenses.Multiple copies of these arrays are formed by molding or embossing froma master lens array.

Current thin film PV modules manufactured are plagued by poorreliability of their panels. This is caused by the breakdown of the filmover time due to absorption of UV light that breaks down unsaturatedbonds in the polymers and chemicals causing a reduction in efficiency.Optical films developed by the inventive process could be used to filterout the UV light without attenuating the other part of the lightspectrum before delivering the light to the PV panel.

Most of the sub-micron devices fabricated is 2D in nature. Fabricationof curved side walls which is required to manufacture micro-lens is alsovery difficult with existing art. By introducing an extra dimension intothe fabrication process will enable designers to exploit extra surfacesfor novel applications.

-   -   1) This would mean that compound micro-lens with custom designed        curvature can be produced.    -   2) From these devices, functional films with novel applications,        such as for collecting, transporting and manipulating light can        be fabricated.

The mold made by this inventive process not only enable fabrication ofsmall devices with curved side walls but allows stamping of the moldonto softer material, fabricating shapes such as non-spherical andspecially designed lens, with curvatures not limited by the propertiesof the surface tensions of the liquid used for making micro-lens.

Such optical films are of interest to solar PV manufacturers, as thesefilms can be incorporated onto the surface of the thin film or glass toreduce reflection, total internal reflection, collect light and focusingit onto the active devices. Although direct application of film on PVpanel is able to provide a modest incremental in efficiency, this filmcould also function like a light collector. This is done by collectinglight at on the flat surface, bend it such that total internalreflection conditions are met within the film and guide the lightthrough the film, finally emitting through the edge of the film. Theintensity of the light emitted at the edge of the film will be a directfunction of surface area of film. By incorporating films to collectlight and piping it to the PV, the PV will be exposed to more light thanpreviously possible. These films are flat, low cost and could bedeployed into onto any surface to collect light and delivering it to PVpanels that might otherwise not optimally positioned to absorb light.(e.g. urban areas)

Besides using the functional films in the solar PV industries, otherapplications include display technologies.

-   -   1) With such functional films it can be applied in solar power        generation by, collecting, delivering, and focusing onto PV        panels. The PV panels could be installed in such a way, that it        is not exposed to extreme weather conditions, while providing        light energy of many suns to the PV films of comparable surface        area.    -   2) These films could also be designed as optical film, to        deliver and focus light onto the pixels of LCD screens and        flexible electronic applications,

When such films are applied to the PV module light it serves severalfunctions, 1) anti-reflection film, 2) collect light, 3) transport lightand 4) focus/concentrate light. This will maximize the amount of lightcollected absorbed on to the PVs. This would mean high PV efficiencies,easier panel installations and much lower cost.

The micro-lens manufactured by this inventive process can be used forchanneling light from the exterior into the interior of buildings.

Other Applications

Simple single layer process have many applications such as fabricatingnon-symmetric micro grating for LCD applications, miniaturization ofoptical components for communications, and micro lens to focus lightonto photovoltaic device for efficient collection of light in greenenergy applications.

ADVANTAGEOUS EFFECTS OF THE INVENTION

By combining 2D lithography and nanoimprint technology, high resolutionsub micron 3D molds of each layer of 3D structures can be fabricated, atlow cost. Each layer is then built to form the 3D structure. Besides theapplications discussed herein like organ/tissue engineering, many newapplications of nanoimprint such as LCD monitor industry, contact lensindustry, surface texturing of plastic products, semi conductor industryand hard drive industry and even counterfeiting technology can use theinventive process.

1. A process of manufacturing a 3D mold to fabricate a high-throughputand low cost sub-micron 3D structure product, said process integrating2-photon lithography and nanoimprinting, comprising using 2-photon laserlithography and 3D write technology to make a 3D mold of each layer ofthe 3D structure product, using nanoimprinting to form a sheet ofpolymer film of each layer of the 3D structure from said 3D mold of thatlayer, and fabricating each layer to make the sub-micron 3D structureproduct.
 2. A 3D mold of a layer of a high-throughput and low costsub-micron 3D structure product, wherein the 3D mold of the layer iscreated by a process comprising using 2-photon laser lithography and 3Dwrite technology to make a 3D mold of each layer of the 3D structureproduct and using nanoimprinting to form a sheet of polymer film of eachlayer of the 3D structure to make the 3D mold of that layer of thesub-micron 3D structure product.
 3. A 3D mold of a layer of ahigh-throughput and low-cost sub-micron 3D structure product using aprocess which integrates 2-photon lithography and nanoimprinting,wherein the 3D mold of the layer is manufactured by a processcomprising: creating a design of a 3D layer of the 3D structure; settingup a writing process to produce an 3D image of the layer of the 3Dstructure product using a 2-photon lithography tool; developing a photoresist/polymer of the 3D image of the layer on a substrate; sputteringone or more layers of metal onto the surface of the photoresist/polymerof the 3D image of the layer to form a seed metal layer; andtransferring the 3D polymer image coated with the seed metal layer by anelectroplating process to form a 3D metal mold; wherein the 3D metalmold is used to manufacture a copy of the 3D image of the same layer ofthe 3D structure product.
 4. The 3D mold of a layer of the sub-micron 3Dstructure product as claimed in claim 3, wherein the step of creating adesign of a 3D layer includes anchoring the base of 3D CAD at thesurface of the substrate, compensating for polymer shrinking and makingit mechanically strong to prevent the sub micron 3D structure fromcollapsing during the rinsing and drying process.
 5. The 3D mold of alayer of the sub-micron 3D structure product as claimed in claim 3,wherein the 3D image of said layer produced by said writing processcomprises an image from 0.01 micron to 150 microns in thickness.
 6. The3D mold of a layer of the sub-micron 3D structure product as claimed inclaim 3, wherein the 3D image of said layer produced by said writingprocess comprises an image of 100 microns thickness.
 7. The 3D mold of alayer of the sub-micron 3D structure product as claimed in claim 3,wherein the parameters of said layer is used as input for themanufacture of a mold of that layer and wherein said layer is from 0.01microns to 100 microns in thickness.
 8. The 3D mold of a layer of thesub-micron 3D structure product layer as claimed in claim 3, wherein theparameters of said layer is used as input for the manufacture of a moldof that layer and wherein said layer is 100 microns in thickness.
 9. The3D mold of a layer of the sub-micron 3D structure product as claimed inclaim 3, wherein said layer of the 3D image is from 0.01 microns to 150microns in thickness.
 10. The 3D mold of a layer of the sub-micron 3Dstructure product as claimed in claim 3, wherein the step of developinga photo resist/polymer of the 3D image comprises cleaning the substrate,applying a spin coat resist onto the substrate, removing any photoresist on the back of the substrate with a solvent, pre-baking thesubstrate, placing the substrate on a vacuum chuck, turning on thevacuum, aligning a wafer, inputting the process parameters, marking andchecking the substrate to ensure that every device is correctlypositioned and removing the photo resist/polymer of the slice of theimage of that layer of the substrate.
 11. The 3D mold of a layer of thesub-micron 3D structure product as claimed in claim 3, wherein the stepof forming a seed metal layer by sputtering one or more layers of metalonto the surface of the resist/polymer of the image comprises checkingthere are no residues of photoresist or other materials left on thesubstrate, placing the wafer in a sputtering tool, pumping the chamberdown to base pressure, performing a short plasma clean process to ensurethe surface is clean, depositing one or more metallic layers, layer bylayer to form the seed metal layer and removing the wafer from thechamber.
 12. The 3D mold of a layer of the sub-micron 3D structureproduct as claimed in claim 3, wherein the step of transferring of thepolymer image formed from the seed metal layer by an electroplatingprocess to form a metal mold comprises placing the substrate with theseed metal layer in an electroplating bath, setting the electroplatingparameters, plating until the desired thickness is achieved, removingthe wafer from the holder, removing the resist from the 3D mold, rinsingthe mold thoroughly with de ionized water, grinding the back and edgesof the 3D mold to size, rinsing the 3D mold in de ionized water,performing O₂ plasma cleaning on the surface of the 3D mold.
 13. The 3Dmold of a layer of the sub-micron 3D structure product as claimed inclaim 3, wherein the step of transferring of the polymer image formedfrom the seed metal layer by an electroplating process to form a metalmold comprises placing the substrate with the seed metal layer in anelectroplating bath, setting the electroplating parameters, platinguntil the desired thickness is achieved, removing the wafer from theholder, removing the resist from the 3D mold, rinsing the moldthoroughly with de ionized water, cutting the back and edges of the 3Dmold to size, rinsing the 3D mold in de ionized water, and performing O₂plasma cleaning on the surface of the 3D mold.
 14. The 3D mold of alayer of the sub-micron 3D structure product mold as claimed in claim 3,wherein the step of transferring of the polymer image formed from theseed metal layer by an electroplating process to form a metal moldcomprises placing the substrate with the seed metal layer in anelectroplating bath, setting the electroplating parameters, platinguntil the desired thickness is achieved, removing the wafer from theholder, removing the resist from the 3D mold, rinsing the moldthoroughly with de ionized water, punching the back and edges of the 3Dmold to size, rinsing the 3D mold in de ionized water, and performing O₂plasma cleaning on the surface of the 3D mold.
 15. The 3D mold of alayer of the sub-micron 3D structure product as claimed in claim 3,wherein the step of fabricating a mold comprises coating a substratewith photoresist, setting the process parameters for the stamping tool,transferring the 3D image from the metal mold onto a large substratethrough a series of stamp and step sequence, developing the resist afterprocessing, de-laminating the resist/polymer from the substrate,wrapping the substrate over a jig to form a cylinder, electroplating thecylinder until the desired thickness is achieved, grinding and polishingthe cylinder to the correct finish and thickness.
 16. The 3D mold of alayer of the sub-micron 3D structure product as claimed in claim 3,wherein the mold comprises a master mold and secondary molds.
 17. The 3Dmold of a layer of the sub-micron 3D structure product as claimed inclaim 3, comprising making 2 roller molds, wherein a mold is made for anupper surface of a layer of a 3D structure and another mold is made fora lower surface of the same layer of a 3D structure, wherein each layeris then aligned and zipped together to adhere together to form multiplelayer structures.
 18. The 3D mold of a layer of the sub-micron 3Dstructure product as claimed in claim 3, wherein the nanoimprintingprocess includes Thermal NIL or UV NIL or Roll-to-roll NIL.
 19. A 3Dmold of a layer of the sub-micron 3D structure product as claimed inclaim 3, wherein the 2-photon lithography comprises software tofabricate 3D molds of any shape and molds of different shapes which canbe combined to form complex molds.
 20. A 3D mold of a layer of thesub-micron 3D structure product as claimed in claim 3, wherein theinitial template is 3D in shape having curved side walls compared tograyscale structures, which have vertical or sloping side walls.
 21. A3D mold of a layer of the sub-micron 3D structure product as claimed inclaim 2, wherein the mold made of flexible polymer is attached onto thesurface of a cylinder to form a roller of flexible polymer mold, fornanoimprinting.
 22. A 3D mold of a layer of the sub-micron 3D structureproduct as claimed in claim 2, wherein the mold made of sheet metal isattached onto the surface of a cylinder to form a roller of sheet metalmold with polymer features, for nanoimprinting.
 23. A 3D mold of a layerof the sub-micron 3D structure product as claimed in claim 2, whereinthe mold made of sheet aluminum is attached onto the surface of acylinder to form a roller of sheet aluminum mold with metal featuresstamped on using a nickel master mold, for nanoimprinting.
 24. A 3D moldof a layer of the sub-micron 3D structure product as claimed in claim 2,wherein the mold made of sheet metal having metal features electroplatedonto its surface is attached onto the surface of a cylinder to form aroller of sheet metal mold with metal features, for nanoimprinting. 25.A process of manufacturing a 3D mold as claimed in claim 1, wherein theprocess follows the NIL process flow, and comprises: Using improveddesigns in mold manufacturing with library of shapes to establish designrules for mass manufacturing of 3D devices, making molds with these 3Dtemplates and using stamp on NIL thermal, UV, stamping and roll-to-rolltechnology.
 26. A process to manufacture a 3D mold used to fabricate ahigh-throughput and low cost sub-micron 3D structure product,integrating 2-photon lithography and nanoimprinting, comprising using 2photon laser lithography and 3D write technology to make a 3D mold ofeach layer of the 3D structure, using nanoimprinting to form a sheet ofpolymer film of each layer of the 3D structure from the 3D mold, andstacking each layer of the 3D structure to fabricate the sub-micron 3Dstructure product.
 27. The process to manufacture a 3D mold used tofabricate a high-throughput and low cost sub-micron 3D structure productas claimed in claim 26, using 3D write technology to pattern a templatefor the 3D mold.
 28. A process to manufacture a 3D mold used tofabricate a high-throughput and low cost sub-micron 3D structureproducts as claimed in claim 22, wherein nanoimprinting comprisesThermal NIL thermal, UV NIL or Roll-to-Roll nanoimprinting.
 29. Aplurality of 3D molds as claimed in claim 2, used to create a pluralityof layers of 3D structures, said structures selected from the groupconsisting of: a. Organ/tissue scaffolds fabricated by slicing a 3D CADdesign of the scaffold into multiple layers, each layer beingindividually fabricated using nanoimprint to overlay and bond all layersto form the final scaffolds, creating such scaffolds which areanatomically similar to those created in vivo physical environment. b.Tissue engineering scaffolds; and c. medical implantable devices
 30. A3D mold as claimed in claim 2, to fabricate simple 3D structures,wherein a single stamping nanoimprinting process is used.
 31. A 3D moldas claimed in claim 2, to fabricate simple 3D structures, wherein thematerial used in the NIL process comprises either synthetic orbiological material.
 32. A process for the manufacture of scaffolds fortissue engineering, comprising the following steps:— a. creating a 3Dtemplate using 2-photon lithography; b. transferring the 3D image onto a3D mold; c. designing the structures with a computer aided designprogram (CAD); d. using software with the 3D CAD drawing as input toautomatically sliced the said structures into multiple layers; e.eliminating layers with repeated patterns; f. fabricating templates formold making; g. fabricating a master mold for each layer to produce ahard/flexible mold for a stamping/roll-to-roll nanoimprint tool; and h.sandwiching each layer produced onto each other to form a complete organscaffold with physical dimensions close to an actual natural scaffold.33. A process used in the manufacture of medical devices such as bridgesfor nerves and bones requiring physical cues to guide growth of nervesand bones, comprising the following steps:— a. creating a 3D templateusing 2-photon lithography; b. transferring the 3D image onto a mold; c.designing the structures with a computer aided design program (CAD); d.using software with the 3D CAD drawing as input to automatically slicedthe said structures into multiple layers; e. eliminating layers withrepeated patterns; f. fabricating templates for mold making; g.fabricating a master mold for each layer to produce a hard/flexible moldfor a stamping/roll-to-roll nanoimprint tool; and h. sandwiching eachlayer produced onto each other to form a complete organ scaffold withphysical dimensions close to an actual natural scaffold.
 34. A processfor the manufacture of customized micro-lens to form a more functionaloptical film, comprising the following steps:— a. creating a 3D templateusing 2-photon lithography; b. transferring the 3D image onto a mold; c.designing the structures with a computer aided design program (CAD); d.using software with the 3D CAD drawing as input to automatically slicedthe said structures into multiple layers; e. eliminating layers withrepeated patterns; f. fabricating templates for mold making; g.fabricating a master mold for each layer to produce a hard/flexible moldfor a stamping/roll-to-roll nanoimprint tool; and h. sandwiching eachlayer produced onto each other to form a complete optical film madeentirely of compound micro-lens with custom designed curvatures; whereinthe optical film is incorporated onto the surface of a thin film or athin layer of glass to reduce reflection, total internal reflection,collect light and focus the light collected onto active devices.